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81.
For many years halothane and enflurane have been used clinically as volatile anaesthetics, however, their mechanism of action is still not fully understood. Recently, it has been suggested that they can act by a direct bonding to neuroreceptors containing the aromatic groups. In this work, the halothane?benzene and enflurane?benzene complexes were studied by the ab initio MP2 and CCSD(T) methods. All possible structures of the complexes were calculated by means of the counterpoise CP-corrected gradient optimization technique. It has been found that among these species, the C–H?π hydrogen bonded complexes are the most stable. The CCSD(T)/CBS calculated stabilization energies for halothane and enflurane complexes are: −10.56 and −9.72 kcal mol−1, respectively. The interaction energy is mainly dominated by the dispersion attraction. In the case of enflurane, the C–H bond shows a very small contraction (by −0.0008 Å) upon complexation. This change is accompanied by the blue-shift (20 cm−1) of the C–H stretching frequency and an increase of the infrared intensity of the corresponding mode by 7 km mol−1. Similar results were obtained for the halothane complex: a small contraction of the C–H bond; an increase of the C–H stretching frequency by 11 cm−1 (blue-shift); and an increase of the infrared intensity by 37 km mol−1. In order to explain the nature of these effects, the halothane and enflurane molecules were studied in the electric field generated by benzene atoms, and Natural Bond Orbital (NBO) analyses were performed. The molecular dipole moments of these molecules were calculated with respect to the C–H bond changes. The positive dipole moment derivative obtained for halothane is in agreement with the literature data, while, in the case of enflurane, an unusual effect is observed, the blue-shift of the C–H stretching frequency is accompanied by the positive dipole moment derivative for one C–H bond and the negative for the other C–H bond. The mechanisms responsible for contraction and strengthening of the C–H bonds are discussed. 相似文献
82.
Wu B Szymański W Wijma HJ Crismaru CG de Wildeman S Poelarends GJ Feringa BL Janssen DB 《Chemical communications (Cambridge, England)》2010,46(43):8157-8159
By replacing a single active-site residue Cys107 with Ser in phenylalanine aminomutase (PAM), the enzyme gained tyrosine aminomutase (TAM) activity while retaining PAM activity and high enantioselectivity. This engineered enantioselective TAM also catalyzed formation of β-tyrosine from p-coumaric acid and may prove to be useful for the synthesis of enantiopure β-tyrosine and its derivatives. 相似文献
83.
We study the weak hereditary class S
w
(
) of all weak subalgebras of algebras in a total variety
}. We establish an algebraic characterization, in the sense of Birkhoff’s HSP theorem, and a syntactical characterization
of these classes. We also consider the problem of when such a weak hereditary class is weak equational. 相似文献
84.
A general scheme of constructing a canonical structure (i.e. Poisson bracket, canonical fields) in classical field theories is proposed. The theory is manifestly independent of the particular choice of an initial space-like surface in space-time. The connection between dynamics and canonical structure is established. Applications to theories with a gauge and constraints are of special interest. Several physical examples are given. 相似文献
85.
Wiktor Kemula Barbara Behr Joanna Taraszewska 《Journal of Electroanalytical Chemistry》1975,65(2):651-659
It has been shown that a hanging mercury drop electrode of the Kemula type is a very convenient tool for studying the redox processes of organic substances in the positive potential range. Conditions influencing the oxidation process are discussed. The method described may prove to be an analytical tool for the determination of some aromatic amines. 相似文献
86.
87.
Dr. Wiktor Szymański Willem A. Velema Prof. Dr. Ben L. Feringa 《Angewandte Chemie (International ed. in English)》2014,53(33):8682-8686
Photocaged compounds are important tools for studying and regulating multiple processes, including biological functions. Reported herein is the use of the Passerini multicomponent reaction for modular preparation of photocaged carboxylic acids. The reaction is compatible with several functionalities and proceeds smoothly both in water and dichloromethane. The choice of aldehyde determines the wavelength used for deprotection and enables formation of orthogonally protected products. The isocyanide component can be used for introduction of reactive tags and photosensitizers, as well as for immobilization on a solid support. 相似文献
88.
89.
Dr. Anna Grabarz Dr. Mariusz Michalczyk Dr. Wiktor Zierkiewicz Prof. Steve Scheiner 《Chemphyschem》2020,21(17):1934-1944
The pairing of TFH3 with a TH2CH3− anion, where T represents tetrel atoms C, Si, Ge, Sn, Pb, results in a strong direct interaction between the two T atoms. The interaction energy is sensitive to the nature of the two T atoms but can be as large as 90 kcal/mol. The noncovalent bond strength rises quickly as the basic T atom of the anion becomes smaller, or as the Lewis acid T grows larger, although there is less sensitivity to the latter atom. The electrostatic component makes up some 55–70 % of the total attraction energy. This term is well accounted for by simple combination of the maximum and minimum values of the molecular electrostatic potential of the Lewis acid and base units, respectively. The complexation induces a rearrangement in the TFH3 molecule from tetrahedral to trigonal pyramidal. The associated deformation energy reduces the exothermicity of the complexation reaction. Electron density shift patterns reveal a density loss on the basic T atom, along with accompanying increases on the acidic T and its attached F atom. 相似文献
90.
Orthoconic Antiferroelectric Liquid Crystals (OAFLC) are recognised as a promising medium for display and photonic applications due to their unique electrooptical properties. The application of OAFLC is still hampered by a number of parasitic effects deteriorating the electrooptical performance of contemporary available materials. An attempt elaborating of a working OAFLC mixture with the helical pitch longer than the typical cell gap is reported. Using this mixture, near-perfect optical uniformity and excellent dark state at the zero electric field applied were obtained. Basic OAFLC mixture was doped with two homostructural analogues to study the influence of the molecular polarity and chirality on the electrooptical performance and chosen physical parameters. The physical and structural properties of admixtures and their electrooptical performance are presented and discussed. 相似文献